Panel and fastening system for such panel

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a fastening system for rectangular, tabular panels, especially floor panels, comprising retaining profiles disposed on the small faces of said panels. Opposite retaining profiles match said retaining profiles in such a manner that similar panels can be interlinked. The retaining profiles are designed as first retaining profiles on opposite small faces and as second retaining profiles on the remaining small faces, in such a way that, on a panel in a first line, a new panel can be locked in a second line by attaching the new panel to the installed panel at a temporary angle relative to the installed panel and then swiveling it down into the plane of the installed panel, where the opposite second retaining elements display corresponding hook elements and where a hook connection can be established by means of one of the hook elements of the new panel and a hook element of a panel that is already installed in the second line by swiveling down the new panel. Each hook connection is associated with an additional, loose locking element that, in the hooked state of two panels, prevents release of the hook connection in a direction perpendicular to the plane of the installed panels, provided that the locking element is located in a locking groove of one of the hook elements of a first panel and the locking groove is provided on a surface of the hook element that, in the installed state of the panels, is oriented approximately perpendicular to the plane in which the panels are installed.

2. Background of the Art

A fastening system without an additional locking element is known from DE 199 29 896 A1. A characteristic feature of a fastening system of this kind is that the first and second retaining profiles used have very different geometries and that the joining methods of the different types of retaining profile differ greatly as a result. In particular, the second retaining profiles, which are designed as hook elements and joined to form a hook connection, involve a technical problem. While the familiar hook connection effectively prevents floor panels from being slid apart in the plane at right angles to the small faces of the connected panels, it does not afford satisfactory resistance to the hook elements being released in a direction perpendicular to the plane of the installed panels.

A fastening system of this kind is used with preference for so-called laminate flooring that displays a core made of a wood material, such as MDF, HDF or particleboard material. The mechanical retaining profiles are generally milled into the small faces of boards made of wood materials.

Laminate flooring is predominantly laid in floating fashion. To reduce footstep sound, a footstep sound-insulating intermediate layer is usually laid between the base surface and the laminate panels. It is also known for a footstep sound-insulating layer to be permanently attached to the underside of laminate panels that faces the base surface.

The hook connection of the known fastening system is particularly problematic if, in the region of a hook connection, only the panel whose hook element is at the bottom, i.e. facing the base surface, is exposed to a high load. The upper hook element of the adjacent panel, hooked into the bottom hook, is not exposed to loading, as a result of which the load only presses the panel with the hook element at the bottom into the generally soft footstep sound-insulating intermediate layer. The top hook element of the non-loaded panel releases itself from the bottom hook element of the adjacent panel in the process. The hook connection ceases to function, and the function usually cannot be restored.

According to the prior art, undercuts are integrated in the hook connection, by means of which releasing of the hook connection perpendicular to the installation plane of the panels is said to be prevented. These undercuts have, however, proven to be insufficient to afford this kind of fastening element sufficient strength.

A generic fastening system displaying an additional locking element in known from WO 01/51732 A1. Following interlocking of the hook elements, the locking element has to be subsequently inserted at the point of connection. This requires an additional work step. Moreover, fitting of the locking element causes problems if a row of panels is located very close in front of a wall. Insufficient space is then available for the locking element to be inserted at the point of connection.

SUMMARY OF THE INVENTION

The object of the invention is to develop a fastening system that is equipped with a hook connection that does not release itself even when the panel with the bottom hook element is subjected to a load and the upper hook element of the adjacent panel is not loaded.

According to the invention, the object is solved in that each hook connection is associated with an additional locking element that prevents, in the hooked state of two panels, the hook connection from being released in a direction perpendicular to the plane of the installed panels.

This innovative locking element can be a very simple component, for which there are various designs. The locking element can be supplied loose with panels, so that the layer himself can attach it at the envisaged point on the hook element during installation, after hooking the hook elements together or it can be already pre-mounted for the layer when he installs the panels. Consequently, the layer does not have to work with any loose connecting parts. Alternatively, a locking element can be integrated into the core material of the panel.

In a particularly simple embodiment, each of the hook elements of the opposite small faces of a panel displays a locking groove extending in the longitudinal direction of the small face. When the hook elements are connected, the locking grooves of two panels are adjacent to each other, forming a common locking recess. When profiling the hook elements with milling tools, the locking grooves can be included in the milling process very easily. Appropriate contours must be provided on the milling tools for this purpose.

If the locking recess has a round or rectangular cross-section, this has the advantage that particularly inexpensive standard material can be used for the locking elements. Any desired material is open to consideration for locking elements with a round or rectangular cross-section. Corresponding rod material can, for example, be purchased in ready-made form, or by the metre for cutting into locking elements of appropriate length. For locking grooves that together form a locking recess with a round cross-section, it is particularly favorable if a nail is used as the locking element, or if the locking element is designed in the manner of a nail. The head of a nail facilitates not only insertion of the locking element into the hook connection during installation, but also removal of the locking element if the hook connection needs to be released again for the purpose of disassembling the panels.

It is very useful if, in the hooked state of two panels, the locking element can simply be inserted into the locking recess wherein the cross-section of the locking element at least partially protrudes into the cross-section of the locking groove of the one panel and partially into the cross-section of the locking groove of the other panel. The division of the cross-section between the locking grooves can be selected virtually at random. It can, for example, be made dependent on whether one of the hook elements in which the locking groove is located is designed more stably than the other. The locking element can be inserted into the locking recess by sliding or hammering. The tolerances of the locking element and the locking recess can be designed in such a way that the locking element can be inserted into the locking recess either loosely or tightly.

Preferably, when a simple locking element with a round or polygonal cross-section is involved, it is advantageous for the locking grooves to be provided on hook element surfaces that, in the installed state of the panels, are oriented roughly perpendicular to the plane in which the panels are installed.

An alternative design of a fastening system with hook elements provides for each panel, in installed state, to display undercut bottom recesses on the underside facing the base surface, at least one of which is located in the region of each hook element on the underside of the panel.

The handling can be improved if, in the connected state of two panels, the undercut of the bottom recess of a first panel is oriented in the opposite direction to the undercut of the bottom recess of a second panel. For the fastening system design with bottom recesses in the region of the hook elements, the locking element is expediently designed as a U-shaped clip that, in assembled state, engages the undercut of the bottom recess of the first panel and the undercut of the bottom recess of the second panel.

In a third alternative for a fastening system, the locking element is located in a locking groove of one of the hook elements of a first panel and displays a resilient snap tab. In this context, a locking groove of the associated hook element of the opposite small face of a second panel forms an undercut snap-in depression, into which the snap tab of the hook element of the first panel snaps automatically during installation.

This design can be provided straightforwardly with a locking element displaying a snap tab projecting far beyond the small face in relaxed state, which snap tab comes into contact with the hook element of the adjacent panel during downward swiveling of a new panel into the plane of the installed panels and is automatically bent so far back that the snap tab no longer projects beyond the outer end of the hook element on the small face. When the hook connection has almost reached its locking position, the snap tab automatically springs forwards into the snap-in depression of the hook element of the adjacent panel, locking the hook connection in the vertical direction, i.e. perpendicular to the plane of the installed panels.

An automatic snap element of this kind can be pre-mounted in one of the hook elements, or enclosed separately so that the layer can attach it to the envisaged hook element himself during installation of the panels.

The automatic locking element and the snap-in depression are expediently designed in such a way that the locking element can easily be pulled out of the hook connection in the longitudinal direction of the small faces at any time using a simple tool, such as pointed pliers, if the panels need to be disassembled. To this end, a free space is provided on either side of the snap tab, so that pliers can be applied.

The fundamental advantage of locking by means of a snap-in locking element, as opposed to a locking element to be slid in, is that no space is required in front of the small face of a row of panels for positioning the locking element against a locking recess and sliding it into said recess. Close to a wall, a locking element that needs to be slid in can no longer be inserted into a locking recess, whereas the snap-in locking element can easily be attached laterally to one of the hook elements and locked by swiveling down a new panel.

A fourth alternative for the fastening system provides for the locking element to be designed as a claw component which, in installed state, is located between interlocking hook surfaces of the hook elements. The claw component has claw elements that grip into the surface of the hook surfaces and prevent vertical separation of the hook elements.

Preferably, a space for the claw component is provided between the interlocking hook surfaces in order to avoid excessive constraining forces between the hook elements.

Furthermore, it is useful if the claw component is locked in a recess provided in the hook element for this purpose and, in the assembled state of the hook connection, adapts to the hook element, starting at the recess and extending over the hook surface.

Straightforwardly, the recess for the claw component can be located on the part of the hook element that engages the corresponding hook element, where the opening of the recess is located on a surface of the hook element that faces the base surface and where, in the assembled state of the hook connection, the claw component is bent in such a way that it projects between the engaging hook surfaces.

Handling of the claw component is facilitated by the fact that it is of L-shaped design and that a first leg of the L-shaped claw component can be inserted in the recess of the hook element and a second leg, provided with the claw elements, points in the direction of the hook surface of the same hook element. In this context, the latter leg is automatically bent into the space between the engaging hook surfaces during installation.

The purpose of a further useful improvement is that one and the same locking recess formed by locking grooves of two hook elements can serve to accommodate different locking elements that display different geometries and afford the hook connection the necessary strength by means of different locking mechanisms. The locking grooves and locking elements are specially coordinated with each other to this end. In this context, either a rod-shaped locking element can be slid into the locking recess in its longitudinal direction or, alternatively, a locking element displaying a resilient snap tab can be accommodated in the same locking recess, where one of the locking grooves then forms a retaining mount for the locking element provided with the snap tab, and the associated locking groove forms an undercut snap-in depression that the resilient snap tab engages automatically during assembly of the hook connection.

A panel with a fastening system according to the invention displays two different types of interacting retaining profiles. The retaining profiles via which the individual rows of a laid floor are interlocked display retaining profiles that are interlocked according to the principle of inclined attachment of a new panel with subsequent downward swiveling of the same. The type of retaining profile required for this makes it possible to mechanically interlock a new panel on a row of installed panels by means of a hinge-like swiveling movement. As a result, the individual panel rows are protected against being pulled apart in the plane in a direction perpendicular to the interlocked retaining profiles.

On the remaining two small faces of the panel, retaining profiles are provided in the form of hook elements, where a first hook element projects from the small face and, in the installed state, faces the base surface, and the second hook element projects from the small face and faces the decorative top side of the panel. Both hook elements of a hook connection are protected against moving apart in a direction perpendicular to the plane of the installed panels by an additional locking element.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the invention is illustrated below in a drawing and described in detail on the basis of the Figures. The Figures show the following:

<figref idref="DRAWINGS">FIG. 1</figref> A perspective view of a retaining profile that can be mechanically interlocked by attaching a new panel at an angle and subsequently swiveling it down into the plane of the installed panels,

<figref idref="DRAWINGS">FIG. 2</figref> The attachment at an angle of the retaining profiles according to <figref idref="DRAWINGS">FIG. 1</figref>,

<figref idref="DRAWINGS">FIG. 3</figref> The retaining profiles according to <figref idref="DRAWINGS">FIG. 1</figref> in the interlocked state,

<figref idref="DRAWINGS">FIG. 4</figref> Retaining profiles in the form of hook elements according to the prior art,

<figref idref="DRAWINGS">FIGS. 5-10</figref> Embodiments of a hook connection with one or more additional locking elements with a rectangular cross-section,

<figref idref="DRAWINGS">FIGS. 11-14</figref> A design of a hook connection with one or more additional locking elements displaying a round cross-section,

FIGS. <b>15</b>/<b>16</b> Embodiments of a hook connection with locking elements that, in the installed state of the panels, are recessed into hook element surfaces that lie in a roughly horizontal position,

<figref idref="DRAWINGS">FIG. 17-20</figref> An embodiment of a hook connection with a locking element with a resilient snap tab that automatically engages an associated snap-in depression during assembly of the hook connection,

<figref idref="DRAWINGS">FIG. 21</figref> A hook connection with a locking element designed as a claw component,

<figref idref="DRAWINGS">FIG. 22</figref> A hook connection with a locking element designed as a clip on the underside of the panels,

<figref idref="DRAWINGS">FIG. 23</figref> A further locking element with a resilient snap tab and a locking groove adapted to accommodate the locking element,

<figref idref="DRAWINGS">FIG. 24</figref> A hook connection with the locking element according to <figref idref="DRAWINGS">FIG. 23</figref> during the connecting procedure,

<figref idref="DRAWINGS">FIG. 25</figref> A hook connection with the locking element according to <figref idref="DRAWINGS">FIG. 23</figref> in engaged state,

<figref idref="DRAWINGS">FIG. 26</figref> A hook connection with the same locking grooves and the same locking recess as according to <figref idref="DRAWINGS">FIG. 25</figref>, where the snap tab locking element is replaced by a locking element with a round cross-section.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

<figref idref="DRAWINGS">FIG. 1</figref> of the drawing shows a perspective view of one type of retaining profile for fastening system <b>1</b> according to the invention. The opposite small faces of panels <b>2</b> and <b>3</b> are provided with corresponding retaining profiles, so that adjacent panels <b>2</b> and <b>3</b> can be connected to each other. This type of retaining profile is a modified tongue-and-groove joint, where tongue <b>4</b> engages an undercut in the lower groove wall of groove <b>5</b>, so that, in the installed state, the two panels <b>2</b> and <b>3</b> are protected against being pulled apart in the plane of installed panels <b>2</b> and <b>3</b> and perpendicular to the direction of the interlocked small faces.

<figref idref="DRAWINGS">FIG. 2</figref> shows the attachment of a new panel <b>2</b> at an angle. In this context, tongue <b>4</b> of new panel <b>2</b> is always engaged with groove <b>5</b> of installed panel <b>3</b> in the direction of arrow P<b>1</b>, and new panel <b>2</b> is subsequently swiveled down onto base surface V until the position illustrated in <figref idref="DRAWINGS">FIG. 3</figref> is reached. It is easily comprehensible that a curved area <b>4</b><i>a </i>of the cross-section of tongue <b>4</b> engages a depression Sa with a curved cross-section in bottom groove wall <b>5</b><i>b </i>of groove <b>5</b> in such a way that panels <b>2</b> and <b>3</b> are prevented from being slid apart in the plane perpendicular to the interlocked small faces.

The remaining small faces of a panel <b>2</b> or <b>3</b>, equipped with fastening system <b>1</b> according to the invention, are provided with corresponding retaining profiles with hook elements <b>6</b> and <b>7</b>. These have the advantage that they hook into each other simultaneously, as it were, with the interlocking of the retaining profiles described according to <figref idref="DRAWINGS">FIGS. 1 to 3</figref>, tongue <b>4</b> and groove <b>5</b>, following attachment at an angle, as a result of new panel <b>2</b> being swiveled down onto base surface V. No lateral joining movement of any kind whatsoever is necessary to establish resultant hook connection <b>8</b>.

Hook connection <b>8</b>, illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, disengages. This occurs, for example, on uneven substrates, where there is air between the panels and base surface V, and also when a soft, footstep sound-insulating intermediate layer <b>9</b> is located between the panels and base surface V. The symbolically represented weight <b>11</b> in <figref idref="DRAWINGS">FIG. 4</figref> illustrates how a panel whose hook element faces the base surface sinks into soft, footstep sound-insulating intermediate layer <b>9</b> when exposed to the load of weight <b>11</b>. This results in vertical offset <b>12</b> at the surface of panels <b>2</b> and <b>10</b>.

<figref idref="DRAWINGS">FIGS. 5 to 10</figref> illustrate different embodiments of hook connections <b>8</b>, all of which are interlocked with an additional locking element <b>13</b>. Locking element <b>13</b> prevents hook connection <b>8</b> moving apart in a direction perpendicular to the plane of installed panels <b>2</b> and <b>10</b>. Even when loaded in accordance with <figref idref="DRAWINGS">FIG. 4</figref>, additional locking element <b>13</b> prevents vertical offset of hooked panels <b>2</b> and <b>10</b>. Locking element <b>13</b> has a rectangular cross-section in the embodiments in <figref idref="DRAWINGS">FIGS. 5 to 10</figref>. Locking grooves <b>14</b> and <b>15</b> are provided to accommodate locking element <b>13</b> and, in the hooked state of hook elements <b>6</b> and <b>7</b>, are positioned exactly opposite each other in such a way that a common locking recess <b>16</b> is formed, into which locking element <b>13</b> is inserted in a direction perpendicular to the drawing plane shown. The embodiment according to <figref idref="DRAWINGS">FIG. 5</figref> shows a free space <b>17</b> between the free end of hook element <b>7</b>, which faces base surface V, and the small face of associated panel <b>2</b>.

In <figref idref="DRAWINGS">FIG. 6</figref>, on the other hand, no clearance is provided at the same point. Instead, an undercut connection <b>18</b> is provided here, which likewise interlocks in a direction perpendicular to the plane of installed panels <b>2</b> and <b>10</b>. On panel <b>2</b>, whose hook element <b>6</b> faces the surface, a freely projecting surface of the small face of hook element <b>6</b> displays locking groove <b>14</b>, while locking groove <b>15</b> of opposite hook element <b>7</b> of hook connection <b>8</b> is provided on a receding surface <b>19</b> of hook element <b>7</b>. The same applies to the embodiment according to <figref idref="DRAWINGS">FIG. 6</figref>.

<figref idref="DRAWINGS">FIGS. 7 and 8</figref> show examples of a hook connection <b>8</b>, where the small face is provided with additional locking element <b>22</b> accommodated in locking groove <b>15</b> on freely projecting surface <b>20</b> of hook: element <b>7</b>, which faces base surface V. Accordingly, locking groove <b>14</b> on corresponding hook element <b>6</b> is located on receding surface <b>21</b> of hook element <b>6</b> on the small face of panel <b>2</b>. <figref idref="DRAWINGS">FIG. 7</figref> shows an example where hook elements <b>6</b> and <b>7</b> display a free space <b>17</b> in the region of locking element <b>22</b>. In contrast, according to <figref idref="DRAWINGS">FIG. 8</figref>, no free space is provided between hook elements <b>6</b> and <b>7</b> in the region of locking element <b>22</b>. Instead, undercut connection <b>18</b> increases the resistance of hook connection <b>8</b> to being pushed apart in a direction perpendicular to the plane of installed panels <b>2</b> and <b>10</b>.

<figref idref="DRAWINGS">FIGS. 9 and 10</figref> show designs in which each hook connection <b>8</b> is equipped with two locking elements <b>13</b> and <b>22</b>. According to <figref idref="DRAWINGS">FIG. 9</figref>, the positions of locking elements <b>13</b> and <b>22</b> are taken from a combination of <figref idref="DRAWINGS">FIG. 5</figref> and <figref idref="DRAWINGS">FIG. 7</figref>. In <figref idref="DRAWINGS">FIG. 10</figref>, the positions of locking elements <b>13</b> and <b>22</b> are taken from a combination of <figref idref="DRAWINGS">FIGS. 6 and 8</figref>. <figref idref="DRAWINGS">FIG. 9</figref> is a further example of a hook connection <b>8</b> where the free end of hook element <b>7</b> facing base surface V displays a space <b>17</b> between it and the small face of hook element <b>6</b> of adjacent panel <b>2</b>, whereas <figref idref="DRAWINGS">FIG. 10</figref> provides an undercut connection <b>18</b> at the same point.

According to <figref idref="DRAWINGS">FIGS. 11 to 14</figref>, locking elements with a round cross-section are provided. According to <figref idref="DRAWINGS">FIG. 11</figref>, an integral locking groove <b>23</b> with a semi-circular cross-section is provided on the outer free end of hook element <b>6</b>, which faces the upper side of panel <b>2</b>. On corresponding hook element <b>7</b>, a locking groove <b>24</b> is provided accordingly on receding surface <b>19</b> of hook element <b>7</b>, meaning that the two locking grooves <b>23</b> and <b>24</b> together produce locking recess <b>25</b> with a circular cross-section, in which locking element <b>26</b> is located. The same applies to the embodiment according to <figref idref="DRAWINGS">FIG. 12</figref>. In <figref idref="DRAWINGS">FIG. 11</figref>, a free space <b>17</b> is provided between hook element <b>7</b> of the one panel <b>10</b>, which faces base surface V, and a receding surf ace <b>21</b> of hook element <b>6</b> on the small face of adjacent panel <b>2</b>, whereas an undercut connection <b>18</b> is provided at the same point according to <figref idref="DRAWINGS">FIG. 12</figref>.

According to <figref idref="DRAWINGS">FIG. 13</figref>, the location for circular locking element <b>27</b> is, in contrast to <figref idref="DRAWINGS">FIG. 12</figref>, shifted to the free end of hook element <b>7</b> of panel <b>10</b>. Locking groove <b>28</b> of corresponding hook element <b>6</b> is accordingly provided on receding surface <b>21</b> on the small face of adjacent panel <b>2</b>. <figref idref="DRAWINGS">FIG. 13</figref> is an example illustrating that locking element <b>27</b> can be provided at a location where a free space <b>17</b> is provided between the outer free end of bottom hook element <b>7</b> and opposite surface <b>21</b> of corresponding hook element <b>6</b>. An embodiment without free space <b>17</b>, with plane surfaces lying flat against each other, and an embodiment with an undercut connection <b>18</b> according to bottom hook element <b>7</b> in <figref idref="DRAWINGS">FIG. 12</figref>, can likewise be equipped with a locking recess and a locking element <b>27</b>.

<figref idref="DRAWINGS">FIG. 14</figref> illustrates a particularly stable hook connection <b>8</b>, where two locking elements <b>26</b> and <b>27</b> with a circular cross-section are used. The locations of locking elements <b>26</b> and <b>27</b> constitute a combination of the embodiments according to <figref idref="DRAWINGS">FIG. 11</figref> and <figref idref="DRAWINGS">FIG. 13</figref>.

<figref idref="DRAWINGS">FIGS. 15 and 16</figref> show the installed state of panels <b>2</b> and <b>10</b> with completed hook connection <b>8</b>. In this context, locking grooves <b>30</b>, <b>31</b>, <b>32</b>, and <b>33</b> are provided in surfaces that lie roughly parallel to the plane of the installed panels. Again, locking grooves <b>30</b> and <b>32</b> of the one hook element <b>6</b>, and locking grooves <b>31</b> and <b>33</b> of corresponding hook element <b>7</b>, are positioned in such a way that they are exactly opposite each other and together each form a locking recess in which a locking element <b>34</b> or <b>35</b> is located. According to both <figref idref="DRAWINGS">FIG. 15</figref> and <figref idref="DRAWINGS">FIG. 16</figref>, it is possible to dispense with one of locking elements <b>34</b> and <b>35</b>, and the corresponding locking recess, in order to simplify the geometry. Since locking elements <b>34</b> and <b>35</b> have to prevent hook connection <b>8</b> moving apart in a direction perpendicular to the plane of panels <b>2</b> and <b>10</b>, locking elements <b>34</b> and <b>35</b> are designed in such a way that they jam themselves laterally into the groove walls of locking grooves <b>30</b>, <b>31</b>, <b>32</b> and <b>33</b>. In the practical examples illustrated, claw elements <b>34</b><i>a </i>and <b>35</b><i>a </i>are provided for this purpose, projecting from the surface of the locking elements. These claw elements can also be designed in the manner of barbs, where the barbs in the one locking groove <b>30</b> and the barbs in the opposite locking groove <b>31</b> of the same locking recess are oriented in opposite directions. The same applies to the barbs in locking grooves <b>32</b> and <b>33</b>.

A further embodiment of hook connection <b>8</b> is illustrated in <figref idref="DRAWINGS">FIGS. 17 to 20</figref>. <figref idref="DRAWINGS">FIG. 17</figref> shows a loose locking element <b>36</b> with a resilient snap tab <b>37</b>, which is wide open in the relaxed state illustrated. <figref idref="DRAWINGS">FIG. 18</figref> shows the gradual joining of hook connection <b>8</b> according to the direction of arrow P<b>2</b>. In this context, locking element <b>36</b> according to <figref idref="DRAWINGS">FIG. 17</figref> is inserted in a groove <b>38</b> in the freely projecting surface <b>38</b><i>a </i>of upper hook element <b>6</b>. Resilient snap tab <b>37</b> is bent back by the joining movement itself. As soon as hook connection <b>8</b> almost reaches the locking position shown in <figref idref="DRAWINGS">FIG. 19</figref>, snap tab <b>37</b> of locking element <b>36</b> automatically springs into locking depression <b>39</b> of corresponding hook element <b>7</b>. In the position shown, snap tab <b>37</b> is less wide open than in the relaxed position illustrated in <figref idref="DRAWINGS">FIG. 17</figref>, meaning that it permanently exerts spring pressure on locking depression <b>39</b>, thus securely locking hook connection <b>8</b>.

A floor-layer can insert locking element <b>36</b> as a loose element into groove <b>38</b>, provided in upper hook element <b>6</b>, for this purpose, or it can be pre-mounted on hook element <b>6</b> by the manufacturer. Locking element <b>36</b> can extend over the entire length of the small face of a panel, or over only part of the length of the small face. In the practical example, it starts at one end of the small face and extends over half its length.

<figref idref="DRAWINGS">FIG. 19</figref> shows that free spaces are present on both sides of snap tab <b>37</b>. These can be used, for example, to pull locking element <b>36</b> out of hook connection <b>8</b> with the help of pointed pliers, and thus to release hook connection <b>8</b>, for the purpose of disassembling panels <b>2</b> and <b>10</b>.

<figref idref="DRAWINGS">FIGS. 18 and 19</figref> show a design where the outer end of hook element <b>7</b>, which faces base surface V, displays a free space <b>17</b> between it and corresponding hook element <b>6</b>.

A further embodiment of the hook connection with a locking element <b>36</b> displaying an automatic snap tab <b>37</b> is illustrated in <figref idref="DRAWINGS">FIG. 20</figref>. The only difference compared to the embodiment according to <figref idref="DRAWINGS">FIG. 18</figref> and <figref idref="DRAWINGS">FIG. 19</figref> is that the free outer end of hook element <b>7</b> of panel <b>10</b>, which faces base surface V, does not display a free space <b>17</b> between it and corresponding hook element <b>6</b> of connected panel <b>2</b>. Instead, an undercut connection <b>18</b> is again provided, which, just like locking element <b>36</b>, prevents hook connection <b>8</b> from moving apart in a direction perpendicular to the plane of installed panels <b>2</b> and <b>10</b>.

According to <figref idref="DRAWINGS">FIG. 21</figref>, a different design of fastening system <b>1</b> provides a locking element in the form of a claw component <b>40</b>, which, in assembled state, is located between interlocking hook surfaces <b>41</b> and <b>42</b> of hook elements <b>6</b> and <b>7</b>. Claw component <b>40</b> displays claw elements <b>40</b><i>a</i>, which grip into the surface of hook surfaces <b>41</b> and <b>42</b>, preventing vertical separation of hook elements <b>6</b> and <b>7</b>. To create space for claw component <b>40</b> and to avoid constraining forces between hook elements <b>6</b> and <b>7</b>, a free space <b>43</b> is formed between interlocking hook surfaces <b>41</b> and <b>42</b>. <figref idref="DRAWINGS">FIG. 21</figref> shows claw component <b>40</b> in the assembled state of hook connection <b>8</b>. Claw component <b>40</b> is secured in recess <b>44</b> provided for this purpose in hook element <b>6</b> and adapts to hook element <b>6</b>, starting at recess <b>44</b> and extending over hook surface <b>41</b>. Recess <b>44</b> for claw component <b>40</b> is located on the part of hook element <b>6</b> that engages corresponding hook element <b>7</b>, where the opening of recess <b>44</b> is located on a surface <b>45</b> of hook element <b>6</b> that faces the base surface. In this context, claw component <b>40</b> is bent in such a way that it projects into space <b>43</b> formed by interlocking hook surfaces <b>41</b> and <b>42</b>.

Claw component <b>40</b> is of L-shaped design prior to assembly. A first leg of the L-shaped claw component is inserted in recess <b>44</b> of hook element <b>6</b>. The second leg is provided with the claw elements and points roughly perpendicularly away from the small face of panel <b>10</b> prior to assembly. During assembly, the latter leg is automatically bent into space <b>43</b> between interlocking hook surfaces <b>41</b> and <b>42</b>.

The final design of the fastening system according to the invention, illustrated in <figref idref="DRAWINGS">FIG. 22</figref>, makes use of a locking element in the form of clip <b>46</b>. For this purpose, every panel <b>2</b> and <b>10</b> has, on its underside facing base surface V, undercut bottom recesses <b>47</b> and <b>48</b>, one of which is located in the region of each hook element <b>6</b> or <b>7</b> on the underside of panel <b>2</b> or <b>10</b>. One clip <b>46</b> engages one bottom recess <b>47</b> and <b>48</b> in each of two adjacent panels <b>2</b> and <b>10</b>. So that clip <b>46</b> prevents hook connection <b>8</b> moving apart in a direction perpendicular to the plane of installed panels <b>2</b> and <b>10</b>, each bottom recess <b>47</b> and <b>48</b> has an undercut. According to <figref idref="DRAWINGS">FIG. 22</figref>, the undercut of bottom recess <b>47</b> of a first panel <b>2</b> is, in the assembled state of two panels, oriented in the opposite direction to the undercut of bottom recess <b>48</b> of a second panel <b>10</b>. Clip <b>46</b> is of U-shaped design. It is obvious that clip <b>46</b> also prevents plane, lateral separation perpendicular to hook elements <b>6</b> and <b>7</b> of the small faces of panels <b>2</b> and <b>10</b>, thus supporting the function of hook connection <b>8</b>.

<figref idref="DRAWINGS">FIG. 23</figref> shows a locking element <b>50</b> with a special cross-section, which can, in practice, be replaced by locking element <b>51</b> shown in <figref idref="DRAWINGS">FIG. 26</figref>. The latter locking element <b>51</b> displays a simple, round cross-section. In addition, <figref idref="DRAWINGS">FIG. 23</figref> shows an empty locking groove <b>52</b>, in which locking element <b>50</b> can be accommodated in captive fashion. This captive design ensures that locking element <b>50</b> cannot fall out of locking groove <b>52</b> during handling of a panel <b>2</b>, and during interlocking of hook connection <b>8</b>, according to the direction of arrow P<b>3</b>. To permit the exchange of locking elements <b>50</b> and <b>51</b>, locking grooves <b>52</b> and <b>53</b>, provided in hook elements <b>6</b> and <b>7</b>, are specially adapted to the geometry of the different locking elements <b>50</b> and <b>51</b>.

Locking element <b>50</b> is a development of locking element <b>36</b>, shown in <figref idref="DRAWINGS">FIG. 17</figref>. It displays a snap tab <b>54</b>, which is shown in wide-open, relaxed state in <figref idref="DRAWINGS">FIG. 23</figref>. On back <b>55</b>, locking element <b>50</b> displays a round form that, according to <figref idref="DRAWINGS">FIG. 24</figref>, matches and fits into locking groove <b>52</b> of hook element <b>6</b>. Locking element <b>50</b> is provided with retaining elements <b>56</b> and <b>57</b>, via which it can be fixed in locking groove <b>52</b> of hook element <b>6</b> in captive fashion. Retaining elements <b>56</b> and <b>57</b> additionally serve to prevent slipping or rotation of locking element <b>50</b> in locking groove <b>52</b> or in locking recess <b>58</b>, formed by locking grooves <b>52</b> and <b>53</b>. In the present embodiment, retaining elements <b>56</b> and <b>57</b> are designed as blunt toes. It can be seen on empty locking groove <b>52</b> in <figref idref="DRAWINGS">FIG. 23</figref> that it has material recesses <b>56</b><i>a </i>and <b>57</b><i>a </i>at the edges of its semi-circular cross-section, these serving to accommodate retaining elements <b>56</b> and <b>57</b>. Dimension A indicated on locking groove <b>52</b> is slightly smaller than dimension B indicated on locking element <b>50</b>. This results in captive clamping of locking element <b>50</b> in locking groove <b>52</b>. In a different embodiment, the retaining elements of locking element <b>50</b> are designed as barbs or claw elements (not shown), which can be fixed in part of the groove wall of locking groove <b>52</b> and hold locking element <b>50</b> in captive fashion on hook element <b>6</b>. The material recesses <b>56</b><i>a </i>and <b>57</b><i>a </i>in locking groove <b>52</b> are not necessary with this design.

<figref idref="DRAWINGS">FIG. 24</figref> Shows the joining procedure for hook connection <b>8</b>. Panel <b>2</b> is swiveled down onto base surface V according to the direction of arrow P<b>3</b>, as a result of which hook elements <b>6</b> and <b>7</b> of panels <b>2</b> and <b>10</b> interlock. It is easily recognizable that locking element <b>50</b> is securely retained in locking groove <b>52</b> while the hook elements are connected in the manner described. As soon as the free end of snap tab <b>54</b> has passed upper edge <b>53</b><i>a </i>of locking groove <b>53</b>, snap tab <b>54</b> automatically springs into locking groove <b>53</b>, which serves as a locking depression for it and locks the hook connection, as illustrated in <figref idref="DRAWINGS">FIG. 25</figref>.

LIST OF REFERENCE NUMBERS

<ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0070"><b>1</b> Fastening system</li><li id="ul0001-0002" num="0071"><b>2</b> Panel</li><li id="ul0001-0003" num="0072"><b>3</b> Panel</li><li id="ul0001-0004" num="0073"><b>4</b> Tongue</li><li id="ul0001-0005" num="0074"><b>4</b><i>a </i>Curved area</li><li id="ul0001-0006" num="0075"><b>5</b> Groove</li><li id="ul0001-0007" num="0076"><b>5</b><i>a </i>Curved depression</li><li id="ul0001-0008" num="0077"><b>5</b><i>b </i>Lower groove wall</li><li id="ul0001-0009" num="0078"><b>6</b> Hook element</li><li id="ul0001-0010" num="0079"><b>7</b> Hook element</li><li id="ul0001-0011" num="0080"><b>8</b> Hook connection</li><li id="ul0001-0012" num="0081"><b>9</b> Footstep sound-insulating intermediate layer</li><li id="ul0001-0013" num="0082"><b>10</b> Panel</li><li id="ul0001-0014" num="0083"><b>11</b> Weight</li><li id="ul0001-0015" num="0084"><b>12</b> Vertical offset</li><li id="ul0001-0016" num="0085"><b>13</b> Locking element</li><li id="ul0001-0017" num="0086"><b>14</b> Locking groove</li><li id="ul0001-0018" num="0087"><b>15</b> Locking groove</li><li id="ul0001-0019" num="0088"><b>16</b> Locking recess</li><li id="ul0001-0020" num="0089"><b>17</b> Space</li><li id="ul0001-0021" num="0090"><b>18</b> Undercut connection</li><li id="ul0001-0022" num="0091"><b>19</b> Receding surface</li><li id="ul0001-0023" num="0092"><b>20</b> Projecting surface</li><li id="ul0001-0024" num="0093"><b>21</b> Receding surface</li><li id="ul0001-0025" num="0094"><b>22</b> Locking element</li><li id="ul0001-0026" num="0095"><b>23</b> Locking groove</li><li id="ul0001-0027" num="0096"><b>24</b> Locking groove</li><li id="ul0001-0028" num="0097"><b>25</b> Locking recess</li><li id="ul0001-0029" num="0098"><b>26</b> Locking element</li><li id="ul0001-0030" num="0099"><b>27</b> Locking element</li><li id="ul0001-0031" num="0100"><b>28</b> Locking element</li><li id="ul0001-0032" num="0101"><b>30</b> Locking groove</li><li id="ul0001-0033" num="0102"><b>31</b> Locking groove</li><li id="ul0001-0034" num="0103"><b>32</b> Locking groove</li><li id="ul0001-0035" num="0104"><b>33</b> Locking groove</li><li id="ul0001-0036" num="0105"><b>34</b> Locking element</li><li id="ul0001-0037" num="0106"><b>34</b><i>a </i>Claw element</li><li id="ul0001-0038" num="0107"><b>35</b> Locking element</li><li id="ul0001-0039" num="0108"><b>35</b><i>a </i>Claw element</li><li id="ul0001-0040" num="0109"><b>36</b> Locking element</li><li id="ul0001-0041" num="0110"><b>37</b> Snap tab</li><li id="ul0001-0042" num="0111"><b>38</b> Groove</li><li id="ul0001-0043" num="0112"><b>38</b><i>a </i>Projecting surface</li><li id="ul0001-0044" num="0113"><b>39</b> Snap-in depression</li><li id="ul0001-0045" num="0114"><b>40</b> Claw component</li><li id="ul0001-0046" num="0115"><b>40</b><i>a </i>Claw element</li><li id="ul0001-0047" num="0116"><b>41</b> Hook surface</li><li id="ul0001-0048" num="0117"><b>42</b> Hook surface</li><li id="ul0001-0049" num="0118"><b>43</b> Space</li><li id="ul0001-0050" num="0119"><b>44</b> Recess</li><li id="ul0001-0051" num="0120"><b>45</b> Surface</li><li id="ul0001-0052" num="0121"><b>46</b> Clip</li><li id="ul0001-0053" num="0122"><b>47</b> Bottom recess</li><li id="ul0001-0054" num="0123"><b>48</b> Bottom recess</li><li id="ul0001-0055" num="0124"><b>50</b> Locking element</li><li id="ul0001-0056" num="0125"><b>51</b> Locking element</li><li id="ul0001-0057" num="0126"><b>52</b> Locking groove</li><li id="ul0001-0058" num="0127"><b>53</b> Locking groove</li><li id="ul0001-0059" num="0128"><b>53</b><i>a </i>Upper edge</li><li id="ul0001-0060" num="0129"><b>54</b> Snap tab</li><li id="ul0001-0061" num="0130"><b>55</b> Back</li><li id="ul0001-0062" num="0131"><b>56</b> Retaining element</li><li id="ul0001-0063" num="0132"><b>56</b><i>a </i>Material recess</li><li id="ul0001-0064" num="0133"><b>57</b> Retaining element</li><li id="ul0001-0065" num="0134"><b>57</b><i>a </i>Material recess</li><li id="ul0001-0066" num="0135"><b>58</b> Locking recess</li><li id="ul0001-0067" num="0136">A Dimension</li><li id="ul0001-0068" num="0137">B Dimension</li><li id="ul0001-0069" num="0138">Direction of arrow</li><li id="ul0001-0070" num="0139">Direction of arrow</li><li id="ul0001-0071" num="0140">P<b>3</b> Direction of arrow</li><li id="ul0001-0072" num="0141">V Base surface</li></ul>